The Assimilation and Modeling Branch (AMB) is home to much of the research
in NOAA/ESRL/GSD on weather model and data assimilation development for both operational forecasting
and research applications
and for impact studies for new observing systems. AMB contributes significantly
to both regional and global model development, and since 2009 also to atmospheric/ocean coupled
models. AMB collaborates strongly with
NCEP, NCAR, other groups in ESRL (and GSD), and other labs and universities.

AMB scientists lead development of the Rapid Refresh (RAP), an hourly updated weather forecast model/assimilation
system that replaced the Rapid Update Cycle (RUC) at NCEP as NOAA's hourly updated model on 1 May 2012.
RAP version 2, a major upgrade, was implemented at NCEP on 25 Feb 2014.
AMB scientists work with colleagues from NCEP, NCAR, and other labs on RAP development.
The RAP differs from the previous RUC in that it uses

a RAP-unique version of the Weather Research and
Forecast (WRF) model, a community mesoscale forecast model with strong contributions
to its development from AMB,

an RAP-unique version of the Gridpoint Statistical Interpolation (GSI) assimilation system, and

The HRRR, a 3-km model initialized hourly with the ESRL-experimental version
of the radar-enhanced 13-km RAP,
provides unique radar-initialized hourly-updated, convection-resolving forecasts, and
runs over a CONUS-wide domain.

AMB scientists lead work with other scientists from NOAA/ESRL toward the development of a new global atmospheric model including the use of the adaptive isentropic-sigma hybrid vertical coordinate successful with the RUC model, accurate finite-volume horizontal grid, and an icosahedral horizontal grid. ESRL collaborates with NCEP/EMC toward application of the FIM model in the NCEP ESMF framework.

AMB is leading the development of a
next-generation coupled weather/air quality numerical prediction system
based upon the WRF model, called WRF-Chem.
Gas-phase chemistry and aerosol processes are tightly coupled to meteorology within the WRF model structure.
Since the model also includes the aerosol direct and indirect effect
in addition to sophisticated microphysics packages,
WRF-Chem can be used for process studies that are extremely relevant for
global change predictions. WRF-Chem has a large international user
base and, in addition to studying global change processes, is used to predict weather,
dispersion, and air quality. ESRL/GSD currently runs inline chemistry versions
for many of its models, including
FIM-chem
,
RR-chem
, and
HRRR-chem
, all with cycling of 3-d aerosol/chemistry variables.

Observation impact studies

AMB has also conducted studies of forecast impact from different observing systems. AMB is currently focused on a multi-year impact study for TAMDAR (Tropospheric Airborne Meteorological Reporting) regional commercial aircraft observations. AMB has previously examined the impact of the NOAA profiler network and the GPS ground-based precipitable water network (developed at NOAA/ESRL/GSD).